In-flight refueling (or air-to-air refueling) is an important method for extending the range of both manned and unmanned aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, precise positioning of a second aircraft (the receiver aircraft, for example) with respect to a first aircraft (the tanker aircraft, for example) is required in order to provide a safe engagement of the first aircraft (and a refueling system carried thereby) with the second aircraft for the dispensing of fuel. The requirement of precise relative spatial positioning of two rapidly moving aircraft makes in-flight refueling a challenging operation.
One conventional system for in-flight refueling is the boom in-flight refueling system. The boom in-flight refueling system typically comprises a rigid boom carried by and lowered from a rear portion of a fuselage of a first aircraft. At one end of the boom is an extendable refueling nozzle and adjacent the extendable refueling nozzle are airfoils, which are controlled by an in-flight refueling system operator onboard the first aircraft. The airfoils provide maneuverability of the boom with respect to an aircraft that is to be refueled (the second aircraft) and allow the in-flight refueling operator to position the boom relative to the second aircraft. First, an operator of the second aircraft must maneuver the second aircraft to within an in-flight refueling position, below and aft of the first aircraft. Upon maneuvering into the in-flight refueling position, the in-flight refueling system operator controls the airfoils to position the boom such that the extendable refueling nozzle of the boom may extended into a refueling receptacle on the second aircraft. The in-flight refueling system operator is responsible for maintaining the position of the boom relative to the refueling receptacle as the refueling nozzle is extended towards the second aircraft. As both the first and second aircraft may be traveling at hundreds of miles per hour through areas of turbulence created both by atmospheric conditions and the aerodynamic forces of the control surfaces of the aircraft, the positioning and maintenance of boom position relative to the refueling receptacle may be extremely difficult. Furthermore, if the refueling nozzle is extended (typically at a rate of 1 to 4 feet per second) while the boom and refueling receptacle are out of alignment, the nozzle may impact the second aircraft at a position other than the in-flight refueling receptacle, thereby possibly causing serious damage the second aircraft and/or causing a serious mid-air accident.
Also, the in-flight refueling system operator (operator) may be responsible for performing a number of tasks other than controlling the boom for an in-flight refueling operation. For instance, the operator may also be tasked with monitoring the progress of several simultaneous in-flight refueling operations involving the first aircraft, such as in cases wherein the first aircraft is carrying multiple pod-mounted in-flight refueling systems and may be capable of refueling several other aircraft simultaneously. In addition, the operator may be tasked with monitoring fuel transfer, adjusting and maintaining a balanced fuel load onboard the first aircraft, monitoring the position of the second aircraft relative to the first aircraft during in-flight refueling operations so as to advise an operator of the first aircraft to avoid collisions and/or other safety hazards, and performing other tasks related to various in-flight refueling operations. These tasks may be complicated further when, for instance, the second aircraft is an unmanned aircraft such as a UAV, wherein an operator of the second aircraft may be non-existent and/or located remotely. In the case of UAV refueling, the in-flight refueling system operator must be especially vigilant for in-flight collisions while at the same time be able to maintain the position of the in-flight refueling boom in relative alignment with a refueling receptacle carried by an unmanned aircraft that may not be able to compensate quickly for turbulence and/or other anomalies that may typically complicate the in-flight refueling operation.
Thus, it would be advantageous to reduce the workload and/or number of tasks for the operator such that the operator may focus on safety issues and advising an operator of the first aircraft of the relative positions of the first and second aircraft during in-flight refueling operations. One possible method for reducing operator workload may include increasing the level of automation in the in-flight refueling operation, by, for instance, at least partially automating the positioning controls of the in-flight refueling system, such as, for instance, control of the airfoils used to position the in-flight refueling boom relative to the second aircraft. Some optical systems have been disclosed for positioning refueling drogues (in probe and drogue in-flight refueling systems) with respect to refueling probes attached to a second aircraft. As refueling drogues, however, have proven relatively unmaneuverable, these systems have not been operationally viable. One such optical system is described in U.S. Pat. No. 5,326,052 to Krispin et al. Other optical systems for positioning objects with respect to reflectors and retro-reflectors have not been easily adapted for use in all types of in-flight refueling systems. Furthermore, these systems do not address the possibility of automating the control of, for instance, a boom in-flight refueling system.
Therefore, there exists a need for an in-flight refueling system that provides an alignment device to align an in-flight refueling boom carried by a first aircraft with a refueling receptacle carried by a second aircraft. There also exists a need for a boom in-flight refueling system that is at least partially automated so as to reduce operator workload wherein the in-flight refueling system may automatically maneuver and maintain the position of an in-flight refueling boom and/or automatically engage an in-flight refueling boom with a refueling receptacle carried by a second aircraft. There also exists a need for an in-flight refueling system that may be capable of maintaining and/or “tracking” an alignment between an in-flight refueling boom and a refueling receptacle such that an extendable nozzle extending from the in-flight refueling boom may safely engage the refueling receptacle carried by a second aircraft.